Book/Report

FZJ-2020-00764

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Potential- und temperaturvariable Experimente zur atomaren Bewegung auf Ag- und Cu-Elektroden in wässrigen Elektrolyten: eine Rastertunnelmikroskopiestudie

Baier, A. S. (Corresponding author)FZJ*

2001
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/24138

Report No.: Juel-3861

Abstract: This thesis deals with the study of the atomic mass transport on the surface of single crystalelectrodes in contact with aqueous electrolytes. The study was performed using timecorrelation functions as a result of a quantitative analysis of equilibrium step fluctuations. Inscanning tunneling microscope images equilibrium step fluctuations give rise to a frizzyappearance of the monoatomic step edges. The experiments discussed were performed onvicinal Ag(111) electrodes in sulfuric acid containing copper ions and on vicinal Cu(111) indiluted hydrochloric acid. The experimental setup and the modifications of the microscope fortemperature variable experiments are presented.Different possible mass transport mechanisms and the characteristic time dependence of thetime correlation function are briefly presented. The mobility at the electrode surface increaseswith temperature and may depend on the applied electrode potential in a liquid environment.An activation energy for the underlying dominant mass transport may be deduced from anArrhenius plot of the increase of the time correlation function, i.e. the increase of the mobilityof atoms on the surface. Given a strong monotonous potential dependence of the stepfluctuations, an activation energy for the dominant mass transport may be obtained from apotential dependent analysis of the time correlation functions at a given temperature.Measurements performed on Ag(111) in sulfuric acid yield a dominant diffusion mechanism,which is mediated by an exchange of silver-atoms with the electrolytic double layer at positivepotentials with respect to the saturated calomel electrode. With increasing electrode potentialan enhanced mobility of atoms manifests itself in a stronger step frizziness of the monoatomicsteps. From a temperature dependent analysis of the step frizziness an activation energy isobtained. This value is comparable to a result obtained from a potential dependent analysis ofthe increase of the time correlation function at increasingly positive potentials.In contrast to Ag(111), equilibrium step fluctuations on an unreconstructed vicinal Cu(111)electrode in diluted hydrochloric acid are independent of the electrode potential in a widepotential range. An increasing electrode potential leads eventually to the formation of an$\sqrt{3}$ x $\sqrt{3}$ - reconstruction of the surface. From the time dependence of the fluctuations aterrace limited diffusion mechanism could be deduced. This special kind of diffusionmechanism was observed experimentally for the first time within the framework of thepresented thesis. Using temperature variable measurements the activation energy for thediffusion mechanism was measured and yield slightly lower value than comparable studiesperfomed under ultrahigh vacuum conditions.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000 ; Retrocat)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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